Genesis for Rare Earth Elements Enrichment in the Permian Manganese Deposits in Zunyi,Guizhou Province,SW China

The Zunyi manganese deposits, which formed during the Middle to Late Permian period and are located in northern Guizhou and adjacent areas, are the core area of a series of large-medium scale manganese enrichment minerogenesis in the southern margin and interior of the Yangtze platform, Southern China. This study reports the universal enrichment of rare earth elements(REEs) in Zunyi manganese deposits and examines the enrichment characteristics, metallogenic environment and genesis of REEs. The manganese ore bodies present stratiform or stratoid in shape, hosted in the silicon–mud–limestones of the Late Permian Maokou Formation. The manganese ores generally present lamellar, massive, banded and brecciated structures, and mainly consist of rhodochrosite, ropperite, tetalite, capillitite, as well as contains paragenetic gangue minerals including pyrite, chalcopyrite, rutile, barite, tuffaceous clay rock, etc. The manganese ores have higher ΣREE contents range from 158 to 1138.9 ppm(average 509.54 ppm). In addition, the ΣREE contents of tuffaceous clay rock in ore beds vary from 1032.2 to 1824.5 ppm(average 1396.42 ppm). The REEs from manganese deposits are characterized by La, Ce, Nd and Y enriched, and existing in the form of independent minerals(e.g., monazite and xenotime), indicating Zunyi manganese deposits enriched in light rare earth elements(LREE). The Ce_(anom) ratios(average-0.13) and lithofacies and paleogeography characteristics indicate that Zunyi manganese deposits were formed in a weak oxidation-reduction environment. The(La/Yb)_(ch), Y/Ho,(La/Nd)_N,(Dy/Yb)_N, Ce/Ce* and Eu/Eu* values of samples from the Zunyi manganese deposits are 5.53–56.92, 18–39, 1.42–3.15, 0.55–2.20, 0.21–1.76 and 0.48–0.86, respectively, indicating a hydrothermal origin for the manganese mineralization and REEs enrichment. The δ~(13) C_(V-PDB)(-0.54 to-18.1‰) and δ~(18) O_(SMOW)(21.6 to 26.0‰) characteristics of manganese ores reveal a mixed source of magmatic and organic matter. Moreover, the manganese ore, tuffaceous clay rock and Emeishan basalt have extremely similar REE fractionation characteristic, suggesting REEs enrichment and manganese mineralization have been mainly origin from hydrothermal fluids.     

ORE DEPOSITS OF CHINCHUANTANG,CHENHSIEN,HUNAN

I.INTRODUCTION The ore deposits of Chinchuantang were known to geologists sincethe publication of the report by Mr.H.C.Wang~1 and others in theyear of 1930.In this region a great number of different ores includingzinc,lead,arsenic,sulphur,manganese,tungsten and bismuth have been     

Study on the element geochemical charactersitics of the Shazi large-sized anatase ore deposit in Qinglong,Guizhou Province

The Shazi anatase ore deposit in Qinglong, Guizhou Province, is a large-sized anatase deposit that has been recently explored. The characteristics of major oxides in the ore are similar to those of modem laterite weath- ering crust and laterite in the laterite-type gold deposits in the western part of Guizhou Province. Studies on the REE characteristics of basalts and anatase ores in the study region showed that both of them do have extremely strong affinities. There are two groups of trace elements in the ores, i.e., Au-Ag-As-Sb-Hg-Tl association and Sc-TiO2-Cu-Fe-Mn association, reflecting that the formation of anatase ore is related to the formation of siliceous claystone at the early stage of eruption of the Emeishan basaltic magma. The siliceous claystones are the major country rocks for the formation of laterite-type gold ores and anatase ores. In the region anatase ores are rich in Sc and the basalts enriched in Fe, Mn, Ti and Sc are the material source of metallogenesis.     

长江中下游地区内生铁铜矿床与膏盐的关系

A middle-Trlassic sequence of strata composed .of gypsumstlt beds has been reeognized in the middle-lower Yangtze Valley. The mineralization in the gypsum-salt beds is closely related to Yenshanian magmatism, During the Yenshanian, magmatic intrusion activities were very active across evaporite beds, occupying great space in gypsum-salt beds. The magmatie rocks and the alterated country rocks are characterized by alkali-eurichment and halogen-enrichment. Copper and iron ores mainly occur in the evaporite beds or overlying levels. The genesis of endogenic copper and iron ores is commonly considered to be the consequence of interaction of magma with the gypsumsalt beds, i.e. there exists a close genetic connection between evaporites, magmatism and copper-iron ores. These observed features are of great significance both in practice and theory.     

The Major Ore Clusters of Super-Large Iron Deposits in the World,Present Situation of Iron Resources in China,and Prospect

Abstract: The metamorphosed sedimentary type of iron deposits (BIF) is the most important type of iron deposits in the world, and super-large iron ore clusters of this type include the Quadrilatero Ferrifero district and Carajas in Brazil, Hamersley in Australia, Kursk in Russia, Central Province of India and Anshan-Benxi in China. Subordinated types of iron deposits are magmatic, volcanic-hosted and sedimentary ones. This paper briefly introduces the geological characteristics of major super-large iron ore clusters in the world. The proven reserves of iron ores in China are relatively abundant, but they are mainly low-grade ores. Moreover, a considerate part of iron ores are difficult to utilize for their difficult ore dressing, deep burial or other reasons. Iron ore deposits are relatively concentrated in 11 metallogenic provinces (belts), such as the Anshan-Benxi, eastern Hebei, Xichang-Central Yunnan Province and middle-lower reaches of Yangtze River. The main minerogenetic epoches vary widely from the Archean to Quaternary, and are mainly the Late Archean to Middle Proterozoic, Variscan, and Yanshanian periods. The main 7 genetic types of iron deposits in China are metamorphosed sedimentary type (BIF), magmatic type, volcanic-hosted type, skarn type, hydrothermal type, sedimentary type and weathered leaching type. The iron-rich ores occur predominantly in the skarn and marine volcanic-hosted iron deposits, locally in the metamorphosed sedimentary type (BIF) as hydrothermal reformation products. The theory of minerogenetic series of mineral deposits and minerogenic models has applied in investigation and prospecting of iron ore deposits. A combination of deep analyses of aeromagnetic anomalies and geomagnetic anomalies, with gravity anomalies are an effective method to seeking large and deep-buried iron deposits. China has a relatively great ore-searching potential of iron ores, especially for metamorphosed sedimentary, skarn, and marine volcanic-hosted iron deposits. For the lower guarantee degree of iron and steel industry, China should give a trading and open the foreign mining markets.     

Bauxite Deposits in China

Bauxite deposits in China,rangin in age from Late Paleozoic to Cenozoic ,are distributed mainly in Shanxi,Shandong Henan,Guizhou,Guangxi and Yunnan.Based on stratigraphic relations they can be clas-sified as 6 types:inter-system marine,inter-system continental,intra-system marine,intra-system continent-tal,weathering lateritic and weathering accumulation types.But in terms of depositional environments,only four types are distinguished,I.e.the marine deposits,continental deposits,lateritic deposits and weath-ering-accumulation deposits.These deposits have been formed in two steps:firstly,the depression of paraplatform or front basin margins in paleocontinents and secondly,the development of littoral-lagoons on the eroded surface of karstified carbonate bedrocks.The aluminum may have been derived from the carbonate rocks with which the ores are associated,or from adjacent aluminosilicate rocks.     

Geochemistry and Genesis of Iron-apatite Ore in the Khanlogh Deposit, Eastern Cenozoic Quchan-Sabzevar Magmatic Arc, NE Iran

The Khanlogh deposit in the Cenozoic Quchan-Sabzevar magmatic belt, NE Iran, is hosted by Oligocene granodioritic rock. The Khanlogh intrusive body is I-type granitoid of the calc-alkaline series. The orebodies are vein, veinlet, massive, and breccia in shape and occur along the fault zones and fractures within the host rock. Ore minerals dominantly comprise magnetite and apatite associated with epidote, clinopyroxene, calcite, quartz, and chlorite. Apatites of the Khanlogh deposit have a high concentration of REE, and show a strong LREE/HREE ratio with a pronounced negative Eu anomaly. Magnetites have a high concentration of REE and show weak to moderate LREE/HREE fractionation. They are comparable to the REE patterns in Kiruna-type iron ores and show an affinity to calc-alkaline magmas. The Khanlogh deposit is similar in the aspects of host rock lithology, alteration, mineralogy, and mineral chemistry to the Kiruna-type deposits. Field observations, hydrothermal alteration halos, style of mineralization, and the geochemical characteristics of apatite, magnetite, and host rock indicate that these magnetite veins have hydrothermal origin similar to Cenozoic Kiruna-type deposits within the Tarom subzone, NW Iran, and are not related to silica-iron oxide immiscibility, as are the major Precambrian magnetite deposits in central Iran.     

Hydrothermal Mineralization on the Mesoproterozoic Passive Continental Margins of China： A Case Study of the Langshan-Zha＇ertaishan Belt, Inner Mongolia, China

Most ore-forming characteristics of the Langshan-Zha‘ertaishan hydrothermal exhalation belt, which consists of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan large-superlarge Zn-Pb-Cu-Fe sulfide deposits, are most similar to those of Mesoproterozoic SEDEX-type provinces of the world. The characteristics include: (1) All deposits of this type in the belt occur in third-order fault-basins in the Langshan-Zha‘ertaishan aulacogen along the northern margin of the North China Platform; (2) these deposits with all their orebodies hosted in the Mesoproterozoic impure dolomite-marble and carbonaceous phyllite (or schists) have an apparent stratabound nature; ores display laminated and banded structures, showing clear depositional features; (3) there is some evidence of syn-sedimentary faulting, which to a certain extent accounts for the temporal and spatial distribution and the size of the orebodies in all deposits and the formation of intrabed conglomerates and breccias; (4) they show lateral and vertical zonation of sulfides; (5) The Cu/(Pb Zn Cu) ratio of the large and thick Pb Zn Cu orebodies gradually decreases from bottom to top; and (6) barite is interbedded with pyrites and sometimes with sphalerite. However, some characteristics such as the Co/Ni radio of the pyrites, the volcanism, for example, of the Langshan-Zha‘ertalshan metallogenic belt, are different from those of the typical SEDEX deposits of the world. The meta-basic volcanic rock in Huogeqi, the sodic bimodal volcanic rocks in the Dongshengmiao and potassic bimodal-volcanic rocks with blastoporphyfitic and blasto-glomeroporphyritic texture as well as blasto-amygdaloidal structure in the Tanyaokou deposits have been discovered in the only ore-bearing second formation of the Langshan Group in the past 10 years. The metallogeny of some deposits hosted in the Langshan Group is closely related to syn-sedimentary volcanism based on the following facts: most of the lead isotopes in sphalerite, galena, pyrite, pyrrhotite and chalcopyrite plot on both sides of the line for the mantle or between the lines for the mantle and lower crust in the lead isotope composition diagram; cobalt content of some pyrites samples is much higher than the nickel content (Co/Ni= 11.91-12.19). Some volcanic blocks and debris have been picked out from some pyritic and pyrrhotitic ores. All Zn-Pb-Cu-Fe sulfide orebodies in these deposits occur in the strata overlying metamorphic volcanic rocks in the only ore-bearing second formation. In the Jiashengpan deposit that lacks syn-sedimentary volcanic rocks in the host succession only Pb and Zn ores occur without Cu ore, but in the Dongshengmiao, Tanyaokou and Huogeqi deposits with syn-sedimentary volcanic rocks in the host succession Cu ores occur. This indicates a relatively higher ore-forming temperature. The process of synsedimentary volcanic eruption directly supplied some ore-forming elements, and resulted in secular geothermal anomaly favorable for the circulation of a submarine convective hydrothermal system, which accounts for the precipitation of deep mineralizing fluids exhaling into anoxidic basins along the syn-sedimentary fault system in the Langshan-Zha‘ertai rift. The Dongshengmiao, Tanyaokou, and Huogeqi deposits hosted in the Langshan Group appear to be a transitional type of mineral deposit between SEDEX and VMS-types but with a bias towards SEDEX, while the Jiashengpan deposit hosted in the Zha‘ertai Group is of a characteristic SEDEX type. This evidence, together with other new discoveries of Mesoproterozoic volcanic rocks and the features of lithogeny and metallogeny of the Bayun Obo deposit in the neighborhood emphasize the diversity, complexity and uniqueness of the Mesoproterozoic Langshan-Zha‘ertal-Bayun Obo ore belt.     

A Preliminary Review of Metallogenic Regularity of Copper Deposits in China

Copper resources in China are rich, but imported copper products are still required. Researches on metallogenic regularity of major types of copper deposits by geologists have involved in worldwide classification, significant copper belts, representative copper deposits, etc. Studies on metallogenic regularity of copper deposits in China also have made achievements with a long-term work. Combined with latest exploration advances obtained in recent ten years, this review aims to conclude the achievements of researches on copper metallogenic regularity in China. Based on data of 814 copper deposits and other ore (mineralized) occurrences, ten prediction types of copper deposits have been suggested. Porphyry and skarn copper ores are taken as the key targets. Porphyry copper deposits are the most important one which concentrate in Gangdese, Changdu-Sanjiang, Dexing and East Tianshan. The Cenozoic and Mesozoic are the major metallogenic epochs. Four main metallogenic epochs are been studied based on the copper ore geochronological data including Precambrian Era (Archean and Proterozoic), Paleozoic Era, Mesozoic Era and Cenozoic Era. Based on the study of metallogenic series of ore deposits in China, twenty-seven metallogenic series of copper deposits are proposed. This is suggested to deepen the study of metallogenic regularity of copper ore and provide the theory guide for copper resources prediction in China.     

H-O-S-Pb Isotopic Compositions of the Chagele Pb-Zn-Cu-Mo Deposit,Tibet: Implications for the Ore-forming Processes and Comparison with Pb-Zn (Cu-Mo) Deposits in Middle-east Segment of the Nyainqentanglha Metallogenic BeltEI北大核心CSCD

The Chagele is a typical Pb-Zn-Cu-Mo deposit located in the western Nyainqentanglha Pb-Zn-Ag-Fe-Cu metallogenic belt (NPMB) that immediately north of the Gangdese porphyry copper belt, Tibet. The deposit contains three ore types: the porphyry (Cu) Mo ores occur as thin veins hosted in the granite porphyry; the skarn (Cu) Pb-Zn type ores are of vein-type or lenticular-type mainly occurring in the external contact zone and interstratified crack zone; and the hydrothermal vein Pb-Zn type ores are controlled by the NNE-striking faults and situated in the structural fractured zones and the up walls of fault zones. The (Cu) Pb-Zn ores consist mainly of galena, sphalerite, chalcopyrite, pyrite, malachite, showing automorphic granular, hypautomorphic to allotriomorphic granular and metasomatic-relict textures, and exhibiting mainly veined, banded, disseminated and massive structures. Hydrothermal alteration includes skarnization, silicification and limonitization. The (Cu) Mo ores consists mainly of chalcopyrite and molybdenite, and minor pyrite. The (Cu) Mo ores are characterized by scaly texture, veinlet and massive structures. It has reserves of 0.38 Mt Pb, 0.6 Mt Zn and 110.1 t Ag, with average grade of 2.08%, 3.29% and 6.07 g/t, respectively, and is considered as a deposit with huge ore-prospecting potential in western of NPMB. However, the ore-forming material and genesis of the Chagele deposit are still not clear. This paper systematically investigated the H, O, S and Pb isotopes of the Chagele deposit and compared it with the other Pb-Zn (Cu-Mo) deposits in the middle-east segment of NPMB. Isotopic geochemical analyses showed that the fluids have δ18O values of -2.2‰ to 2.9‰ and δD values of -189‰ to -157‰, respectively, indicative of mixing between magmatic and meteoric waters. The bimodal distribution of δ34 S values for sulfides (-5.6‰ to -0.8‰, the average: -3.7‰ and 1.1‰ to 2.6‰, the average: 1.8‰) indicated that sulfur of the ores were derived from both wall rocks and magma, while the Cu-Mo orebodies was mainly derived from the granite porphyry. The sulfides have 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values in ranges of 18.614 to 18.688, 15.657 to 15.747 and 38.988 to 39.269; similarly the granite porphyries have 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of 18.663 to 19.058, 15.643 to 15.664, and 39.002 to 39.559, respectively, implying that both of them were originated from the upper crust. The H-O-S-Pb isotopic characteristics of the Chagele deposit are similar to those of the Pb-Zn polymetallic deposits in the mid-east NPMB, suggesting that these deposits have similar ore-forming fluid and material sources. It can be concluded that the Chagele deposit is a typical porphyry type Mo deposit + skarn type-hydrothermal vein type of Cu-Pb-Zn deposit. Moreover, we argue that the mineralization is not only confined to the mid-east NPMB, the western segment of the belt with similar tectonic-magmatism also has high potential of ore mineralization. © 2018, Science Press. All right reserved.     

Nanhuan manganese deposits within restricted basins of the southeastern Yangtze Platform,China: Constraints from geological and geochemical evidence

The Nanhuan manganese deposits in the southeastern Yangtze Platform occur in the black shale series in the lower part of the Datangpo Formation. In order to constrain the genesis of the deposits, a detailed study was undertaken that involved field observations, major and trace element analyses, organic carbon analyses, and isotope analyses (C, O, S). The major findings are as follows. (1) The ore-bearing rock series, morphology of the ore bodies, and characteristics of ores in several deposits are similar. The ore minerals are rhodochrosite and manganocalcite. The gangue minerals are mainly quartz, feldspar, dolomite, and illite. Minor apatite and bastnaesite occur in the manganese ores. (2) The ores are enriched in Ca and Mg, whereas they are depleted in Si, Al, K, and Ti compared to wall rocks. The ores normalized to average Post-Archean Australian shale (PAAS) are enriched in Co, Mo, and Sr. The chondrite-normalized rare earth element (REE) patterns for ores and wall rocks are between those of typical hydrogenous and hydrothermal type manganese deposits. Additionally, the ores have positive Ce anomalies with an average Ce/Ce* of 1.23 and positive Eu anomalies with an average Eu/Eu* of 1.18 (normalized to PAAS). (3) The average content of organic carbon is 2.21% in the samples, and the average organic carbon isotopic value (δ¹³C_V-PDB) is − 33.44‰. The average inorganic carbon isotopic value (δ¹³C_V-PDB) of carbonates in Gucheng is − 3.07‰, while the values are similar in the other deposits with an average of − 8.36‰. The oxygen isotopic compositions (δ¹⁸O_V-PDB) are similar in different deposits with an average of − 7.72‰. (4) The sulfur isotopic values (δ³⁴S_V-CDT) of pyrite are very high and range from + 37.9‰ to + 62.6‰ (average of 52.7‰), which suggests that the pyrite was formed in restricted basins where sulfate replenishment was limited. The sulfate concentrations in the restricted basins were extremely low and enriched in δ³⁴S, which resulted in the very high δ³⁴S values for the pyrite that formed in the manganese deposits. Therefore, a terrigenous weathering origin for manganese can be excluded; otherwise, the sulfate would have been introduced into the basins together with terrigenous manganese, which would have decreased the δ³⁴S values of pyrites. The manganese, which originated from hydrothermal processes, was enriched in the restricted and anoxic basins, and then, it was oxidized to manganese oxyhydroxide in the overlying oxic waters whereby the products precipitated into the sediments. The manganese oxyhydroxide in the sediment was then reduced to Mn^2 + and released to the pore waters during the process of diagenesis. Some organic carbon was oxidized to CO₃^2 −, which made the depletion of ¹³C in manganese carbonates. Therefore, we suggest that the Nanhuan manganese deposits are hydrothermal–sedimentary/diagenetic type deposits.     

四川黑水-平武地区三叠系菠茨沟组锰赋矿层沉积环境及找矿潜力

四川黑水-平武地区位于扬子地块北西缘之可可西里-松潘前陆盆地之松潘边缘海成锰盆地,系四川省重要铁锰成矿带之一。研究区内的三叠系菠茨沟组中已发现了一批大、中型锰矿床。研究区菠茨沟组具有碎屑岩型与碳酸盐型两种沉积类型,锰矿层均产在钙质岩石与碎屑岩交替变化部位。研究表明,陆棚浅海及水下洼地为锰矿沉积的有利环境,极薄层状钙质岩石与碎屑岩沉积相的频繁演替是野外重要的找矿标志。黑水县下口地区和平武县虎牙地区为研究区最有利的锰矿找矿预测靶区。     

Rare Earth Element Enrichment in Late Archean Manganese Deposits from the Iron Ore Group,East India

The major, trace and rare earth element (REE) composition of Late Archean manganese, ferromanganese and iron ores from the Iron Ore Group (IOG) in Orissa, east India, was examined. Manganese deposits, occurring above the iron formations of the IOG, display massive, rhythmically laminated or botryoidal textures. The ores are composed primarily of iron and manganese, and are low in other major and trace elements such as SiO₂, Al₂O₃, P₂O₅ and Zr. The total REE concentration is as high as 975 ppm in manganese ores, whereas concentrations as high as 345 ppm and 211 ppm are found in ferromanganese and iron ores, respectively. Heavy REE (HREE) enrichments, negative Ce anomalies and positive Eu anomalies were observed in post‐Archean average shale (PAAS)‐normalized REE patterns of the IOG manganese and ferromanganese ores. The stratiform or stratabound shapes of ore bodies within the shale horizon, and REE geochemistry, suggest that the manganese and ferromanganese ores of the IOG were formed by iron and/or manganese precipitation from a submarine, hydrothermal solution under oxic conditions that occurred as a result of mixing with oxic seawater. While HREE concentrations in the Late Archean manganese and ferromanganese ores in the IOG are slightly less than those of the Phanerozoic ferromanganese ores in Japan, HREE resources in the IOG manganese deposits appear to be two orders of magnitude higher because of the large size of the deposits. Although a reliable, economic concentration technique for HREE from manganese and ferromanganese ores has not yet been developed, those ores could be an important future source of HREE.     

广东梅县锰矿物质成份的研究

随着我国钢铁工业和化学工业的迅猛发展,对锰矿资源的需求,日益增加.梅县锰矿公司对该县的锰矿地质和锰矿生产做了大量工作.在前人工作的基础上,我们在锰矿资源的调研中,曾对广东省梅县的宝山岗、白沙坪、桃尧大华、宝坑、仙水塘、磔角坑、车陂等地的锰矿体、进行过采样工作.经室内鉴定后、梅县的锰矿石有优质的放电锰矿石和冶金用锰矿石、矿床规模属于中小型.梅县锰矿资源的生产,继续已有20多年的历史,在矿床的质和量方面尚需做更深入的研究,以便为矿山开采和锰矿生产提供更充分的依据.本文是对锰矿物质成分初步研究的部分结果.     

Manganese deposits: Communication 1. Genetic models of manganese ore formation

Major regularities in the formation of manganese rocks and ores have been established on the basis of available published and original data. The proposed genetic classification of main manganese deposits (with model examples) is as follows: sedimentary-diagenetic (Nikopol, Bol’she-Tokmak; Ukraine), (volcanogenic) hydrothermal-sedimentary (deposits of the Atasui area, Kazakhstan; Magnitogorsk Trough, South Urals), epigenetic (catagenetic) (deposits of the Kalahari manganese ore field, South Africa; Usinsk deposit, Kuznetsk Alatau), and supergene (residual, infiltrational, cavern filling, and pisolitic deposits in India, Brazil, South Africa, and Australia). The results suggest the following conclusions: (1) all primary manganese rocks and ores at the known deposits are hydrothermal- and diagenetic-sedimentary formations of marine environments; (2) manganese concentrations achieve the size of deposits at postsedimentary stages of the initial manganiferous sediment and manganese rock transformation (diagenesis, catagenesis, and retrograde diagenesis); (3) indispensable participation of the isotopically light carbon dioxide related to the destruction of organic matter (OM) is a characteristic feature of manganese carbonate formation during diagenesis; and (4) the role of organic carbon in manganese ore formation becomes notable since early stages of Mn accumulation in the Precambrian sedimentary basins (terminal Archean-initial Early Proterozoic).     

Association of manganese ore and phosphorite-bearing facies in sedimentary sequences: Communication 1. Parastereses and parageneses of phosphorus and manganese in Mesozoic-Cenozoic and Upper Paleozoic rocks

It is shown that cooccurrences (parastereses) of chemical elements, minerals, sedimentary rocks, facies, and formations should be distinguished from their parageneses, which represent geological formations related to a single geological process. It has been established that phosphorus is concentrated in sedimentary manganese ores and is not accumulated in volcanosedimentary and hydrothermal deposits. Parageneses of Mn and P in sedimentary deposits are characterized. Parastereses of manganese ore and phosphorite-bearing facies in Oligocene rocks of southwestern Eurasia, Mesozoic and Upper Paleozoic sections of the Urals, and Mesozoic- Cenozoic sequences of Morocco are considered.     

鄂东北早元古代沉积变质锰矿元素矿物组合特征

鄂东北早元古代沉积变质锰矿是我国时代最古老的锰矿之一,是由早元古代锰质碳酸盐岩经区域变质作用而成,后又经风化富集形成工业矿床。由于特殊的地质构造背景和成矿作用的多阶段性,元素和矿物组合复杂,具有独特性。本文研究了各种组分的演变关系和元素集散因素,为锰质碳酸盐岩在高压绿片岩相区域动力变质及其后表生作用中的演变提供了一个实例。     

Specific features and composition of the Akkermanov manganese deposit

New data on the Akkermanov deposit characterized by specific structure and composition of primary (carbonate) and secondary (manganese oxide) ores are presented. Distribution of mineralization in host rocks and weathering crusts is considered. It is shown that manganiferous carbonate rocks, which host orebodies, formed in a marine basin with well-aerated bottom waters. Oxide ores are mainly composed of crystalline pyrolusite produced by multiple processes of the oxidation of manganese compounds. In this respect, the Akkermanov deposit differs drastically from all manganese deposits developed in Russia and Ukraine.     

Geology of massive sulphide deposits in the Spanish-Portuguese Pyrite Belt

The Spanish-Portuguese Pyrite Belt covers a large area in the SW part of the Iberian Peninsula from Seville to the westcoast of Portugal. Total reserves of aprox. 1.000 million tons of massive sulphide ores have an average content of 46% S, 42% Fe, and 2–4% Cu+Pb+Zn. The stratiform sulphide deposits and accompanying manganese mineralizations are of synsedimentary-exhalative origin. They occur in a Lower Carboniferous, geosynclinal, volcanic-sedimentary rock sequence, strongly folded during the Hercynian Orogeny. A brief outline of the regional geology of this ore province is given, and the geology of three mining districts is described: Lousal (Portugal), La Zarza and Tharsis (Huelva Province, Spain). A close relationship between sulphide and manganese ores with the submarine, acid alkaline volcanism is emphasized. Solfataric activity is responsible for the formation of sulphides in the final stages of volcanic extrusions. The ore concentration in big deposits (ore-lenses with up to 100 million tons of massive sulphides) has been due to inflows of sulphide muds and/or detrital sulphides into newly formed depressions of a contineously changing seafloor topography due to volcano tectonic movements.     

Comparison between Datangpo-type manganese ores and modern marine ferromanganese oxyhydroxide precipitates based on rare earth elements

Datangpo-type sedimentary manganese deposits, which are located in northeastern Guizhou province and its adjacent areas, are Mn carbonate-type deposits hosted in black carbonaceous shale that represent a series of medium to large deposits containing a huge tonnage of reserves. PAAS-normalized rare earth element distribution patterns of manganese ores record “hat-shaped” REY (REE + Y) plots characterized by pronounced middle rare earth element enrichment, evident positive Ce anomalies, weak to strong positive Eu anomalies and negligible negative Y anomalies. These REY geochemical characteristics are different from those of country rocks and record the processes and features of sedimentation and diagenesis. Manganese was precipitated as Mn-oxyhydroxide particles in oxidized water columns with the sorption of a certain amount of rare earth elements, subsequently transforming from Mn-oxyhydroxides to rhodochrosite and redistributing REY in reducing alkaline pore-water during early diagenesis. A number of similarities can be observed through a comparison of Datangpo-type manganese ores and modern marine ferromanganese oxyhydroxide precipitates based on their rare earth elements. The precipitation of Datangpo-type manganese ores is similar to that of hydrogenetic crusts and nodules based on their positive Ce anomalies and relatively higher total REY concentrations. However, several differences also exist. Compared to hydrogenetic crusts and nodules, Datangpo-type manganese ores record smaller positive Ce anomalies, lower total REY concentrations, unobvious fractionation between Y and Ho, and weak to strong positive Eu anomalies. These were caused by quicker sedimentary rates in the oxic water columns of the shallower basin, after which pore water became strongly reducing and alkaline due to the degradation of organic matter in the early diagenetic stage. In addition, compared to typical deposits in the world, Datangpo-type manganese ores are similar to hydrogenetic deposits and different than hydrothermal deposits. All of these characteristics of manganese ores indicate that Datangpo-type manganese ores, the principal metallogenic factors of which include oxidation conditions during deposition and reducing conditions during early diagenetic stages, represent hydrogenetic deposits.